1. Field of the Invention
The present invention relates to a liquid composition, a process for cleaning an ink-jet recording head, an ink-jet recorder, a cartridge, and a process for regenerating an ink-jet recording head.
2. Description of the Related Art
Hitherto, a variety of techniques have been proposed as processes for ink-jet recording. Among them, a process for ink-jet recording which includes the step of discharging an ink as ink droplets by action of thermal energy (a so-called bubble-jet recording process) has various advantages. This process is disclosed in, for example, Japanese Patent Laid-Open No. 54-51837. The process can very easily provide high density multi-nozzles, can yield a high quality image at high speed at very low costs, and can even print on sheets of a plain paper without a special coating layer.
In this type of ink-jet recording process, a recorded image is made in the following manner. Specifically, a heater on a recording head is rapidly heated to thereby form a bubble in a liquid on the heater, and the liquid rapidly increases in volume. The rapidly increased volume allows an ink droplet to discharge and fly from a nozzle at the tip of a recording head unit to thereby adhere to a material on which an image is recorded.
When a large quantity of recordings are made according to the above process, the heater on the recording head is heated over and over again to discharge the ink, and decomposed ink, i.e., burnt ink deposits referred to as xe2x80x9ckogaxe2x80x9d, are deposited on the heater. Such phenomena, which is called kogation, deposits may sometimes inhibit an effective transmission of thermal energy of the heater to the ink, resulting in that the amount or rate of the ink droplets is decreased as compared with an early stage of recording or that the ink droplets cannot be discharged. To prolong the discharge life of ink droplets of an ink-jet recording head, the deposition of koga must be minimized, and various ink compositions for this purpose have been proposed.
For example, Japanese Patent Laid-Open No. 3-160070 proposes an ink containing an oxo anion. Phosphates, polyphosphates, phosphoric esters, arsenates, molybdates, sulfates, sulfites, and oxalates are listed as the oxo anions. However, the ink is still insufficient to prolong the discharge life, and demands have been made to further prolong ink discharge life of an ink-jet recording head.
In addition to the deposits of koga, a heater surface of an ink-jet recording head immediately after manufacture has sometimes contaminants contaminated during various steps, and ink discharge property becomes unstable from an early stage of recording. To stabilize the initial discharge property, an aging treatment is proposed, as is disclosed in, for example, Japanese Patent Laid-Open No. 2-78554. However, such an aging treatment may sometimes induce adherence of koga on the heater surface. In this case, the ink discharge is decreased from early stage of recording, and the original or inherent discharge property cannot be exhibited.
As a possible solution to the above problems, Japanese Patent Laid-Open No. 9-29985 proposes a process for cleaning an ink-jet recording head by use of an aqueous solution containing an electrolyte.
After various investigations, the present inventors found that the aforementioned technique described in the Japanese Patent Laid-Open No. 9-29985 can effectively clean an ink-jet recording head. However, as this process cleans the head using an aqueous strong electrolyte solution containing an inorganic ion, the heater is liable to be damaged and must be very carefully handled. To further prolong the life of an ink-jet recording head, the present inventors had a perception of a novel technique that can remove koga formed on the surface of a heater of an ink-jet recording head in a more safe manner or can clean the surface of the heater, while minimizing damage to the heater.
Accordingly, it is an object of the present invention to provide a liquid composition which can clean and remove koga formed in a long-term use of an ink-jet recording head or contaminants contaminated during the manufacture of the ink-jet recording head and which exerts no or minimized influence upon the ink-jet recording head, to thereby prolong the life of the ink-jet recording head.
It is another object of the present invention to provide a process for cleaning an ink-jet recording head, which process can remove koga or contaminants on the surface of an ink-jet recording head while minimizing the influence upon a heater of the recording head.
A further object of the present invention is to provide an ink-jet recording apparatus which can remove koga or contaminants on the surface of an ink-jet recording head while minimizing the influence upon a heater of the recording head, as well as a cartridge for use in the ink-jet recording apparatus.
Yet another object of the present invention is to provide a process for regenerating an ink-jet recording head by cleaning or removing koga or contaminants adhered on a heater of the ink-jet recording head.
Specifically, the present invention provides, in an aspect, a liquid composition including at least one cleaning agent in an effective amount to clean an ink-jet recording head. The cleaning agent is at least one selected from organic acids, salts of organic acids, organic acid esters, and salts of organic acid esters.
In another aspect, the present invention provides a liquid composition for use in removal of adherents on a surface of an ink-jet recording head, the recording head includes a heater and discharges an ink containing a coloring material by action of the heater, and a surface of the heater is covered with an outermost protective layer including at least one of a metal and a metallic oxide. The liquid composition oxidatively decomposes adherents on a surface of the ink-jet recording head by applying energy to the heater in a stage where the heater is in contact with the liquid composition.
In a further aspect, the present invention provides a process for cleaning an ink-jet recording head. This process includes the use of, for example, the aforementioned liquid composition.
The present invention provides, in yet another aspect, a process for cleaning an ink-jet recording head, which ink-jet recording head has a heater, and a surface of the heater is covered with a protective layer including at least one either of a metal and a metallic oxide. This process includes the step of applying energy to the heater in a state where the heater is in contact with the liquid composition.
In another aspect, the present invention provides an ink-jet recording apparatus. The ink-jet recording apparatus includes, for example, a liquid tank filled with the aforementioned liquid composition, an ink tank filled with an ink containing a coloring material, an ink-jet recording head for discharging the ink, a device for supplying the liquid composition and the ink respectively from the liquid tank and the ink tank to the ink-jet recording head, and a valve device for optionally selecting between the supply of the liquid composition and the supply of the ink to the recording head.
In a further aspect, the present invention provides a cartridge for use in cleaning of an ink-jet recording head, which ink-jet recording head has a heater, a surface of the heater is covered with a protective film including at least one of a metal and a metallic oxide. This cartridge is detachably configured with respect to the ink-jet recording head and preserves the liquid composition.
In addition and advantageously, the present invention provides a process for regenerating an ink-jet recording head, which ink-jet recording head has a heater and serves to discharge ink containing a coloring material, the heater is covered with an outermost protective layer on its surface, and the outermost protective layer includes at least one of a metal and a metallic oxide. This process includes the step of applying thermal energy to the heater in a state where the surface of the heater is in contact with the liquid composition.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.